Nintendo used, or attempted to use, various hardware/software, legal, and economic techniques to force publishers to use their cartridges, for which they took a

Nintendo used, or attempted to use, various hardware/software, legal, and economic techniques to force publishers to use their cartridges, for which they took a significant cut of sales. The hardware‐enforced logo mentioned in another comment was one technique, that was an attempt at abusing trademark (not copyright) law to limit third‐party cartridge manufacturers. However, the courts decisively struck that strategy down in Sega v. Accolade. As for economic techniques, there’s a fun story about a third‐party developer named Color Dreams. They released several games, including Crystal Mines, without Nintendo approval, and made their own cartridges. As the story goes, Nintendo threatened to pull their stock from any toy store that sold unlicensed games, and all the stores naturally caved since Nintendo had the most popular titles. Color Dreams saw the writing on the wall, and came up with a strategy to target one market that Nintendo had no hold over: Christian bookstores. Color Dreams rebranded as “Wisdom Tree,” gave all their games a thin Biblical veneer, and started marketing their games heavily to the religious demographic. By all accounts it was a huge success (relatively speaking, for a completely independent publisher). For an example of the results, check out their conversion of Wolfenstein, Super 3D Noah’s Ark (originally for SNES, now on Steam!): https://store.steampowered.com/app/371180/Super_3D_Noahs_Ark/ https://store.steampowered.com/app/371180/Super_3D_Noahs_Ark...